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Thread: Basic control theory

  1. #1
    Automated Home Legend top brake's Avatar
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    Default Basic control theory

    It's back to school time

    There have been a lot of threads and spirited discussion about various aspects of control theory and performance so thought I would share a very useful free course about Basic Control Theory, part of the Steam Engineering Tutorials series from a world leader in steam engineering and heat transfer control.

    I did my apprenticeship with this company and whilst I found college control theory classes to be rather dry and abstract; this Spirax Sarco course really brought the concepts of control to life. Whilst it is rooted firmly in practical application of control theory to steam engineering applications, much is transferable to domestic heating control.

    Enjoy!


    http://www.spiraxsarco.com/Resources...ol-theory.aspx
    Last edited by top brake; 16th March 2015 at 10:05 PM.
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    Interesting. Obvious first question: which described method does Evohome use when combined with BDR91? Is it basic on/off + proportioning time control?

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    Automated Home Legend top brake's Avatar
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    TPI control FAQ

    http://www.honeywelluk.com/documents...0explained.pdf

    All Honeywell electronic heating controls are TPI which is a proportional integral (P+I) type control using time based on off switching.
    Last edited by top brake; 16th March 2015 at 10:57 PM.
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    Automated Home Legend top brake's Avatar
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    On off control FAQ

    http://www.honeywelluk.com/documents/All/pdf/1052.pdf

    This is used for the Honeywell T6360 thermostat found in millions of homes
    Last edited by top brake; 16th March 2015 at 11:14 PM.
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  5. #5
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    Thanks. Does Evohome + BDR91 (on/off) use pure on/off, as described in the On/Off-control FAQ? Or does it use TPI as well?

    And does an old wired Honeywell Round on/off use TPI as well?

    (The I in TPI stands for Integral. Integral is listed under Continuous control (modulating) in the linked spirax documentation. So I'm wondering wether TPI can be used in a on/off situation as well.)
    Last edited by erik; 16th March 2015 at 11:12 PM.

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    Automated Home Legend top brake's Avatar
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    Some test results on the effectiveness of TPI thermostat and TRV carried out at Salford University on behalf of Beama


    http://www.beama.org.uk/download.cfm...205FD2CBECBEB2
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  7. #7
    Automated Home Legend top brake's Avatar
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    Just to clarify

    Honeywell evohome is TPI

    TPI is not an exclusively Honeywell control definition type, if you search google you will find many other heating control manufacturers describing their products as TPI thermostats; this aligned terminology arose approx 5 years ago and prior to that some manufacturers variously used the terms TPI, PI and or fuzzy logic
    TPI is now recognised by government bodies and classified within building regulations standard assessment procedure for energy performance
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    Excellent. And even though Integral (the I from TPI) is listed in the Spirax documentation under 'modulation', does it also apply to on/off control, Robert?

    And do you know wether the Honeywell T87G1006 uses TPI as well (it certainly seems to, but I'd like to be sure)?

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    Quote Originally Posted by top brake View Post
    Some test results on the effectiveness of TPI thermostat and TRV carried out at Salford University on behalf of Beama


    http://www.beama.org.uk/download.cfm...205FD2CBECBEB2
    This article mentions the boiler is set at its maximum temperature for the tests. Is it recommended generally that one's boiler should be set to maximum?

  10. #10
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    Quote Originally Posted by G4RHL View Post
    This article mentions the boiler is set at its maximum temperature for the tests. Is it recommended generally that one's boiler should be set to maximum?
    Heating system design in the UK requires a boiler flow temperature of 75 degress Celsius at an outdoor temperature -3 degrees Celsius for a radiator circuit. Weather compensated systems will modulate the flow temperature down from this point but even on weather compensated systems they will still opereate at 75 degrees at -3...

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